For purposes of packaging a series of articles, it is customary commercial manufacturing practice to enclose the articles in a tube of plastic film with spaces between the articles and to pass this assembly through apparatus which clamps and cuts through the film between adjacent articles and seals together the cut edges on opposite sides of each cut. This is done by clamping means and a cutter blade secured between a pair of heated bars. The inner end of the space between the heater bars that holds the blade receives a heater element which extends parallel to the length of the blade. The film moves over a fixed cutting and sealing pad, is clamped there, and is cut when the blade moves against the film on the pad. The heater bars also move against the pad and seal the cut edges of the film resting on the pad on opposite sides of the blade.
If the articles to be packaged are no more than about 2 1/2 to 3 inches high, it is conventional to have the blade project only a short distance, such as 0.013 to 0.016 inch, beyond the heater bars toward the cutter pad. In that case, it is conventional to use a cutting and sealing pad having a plain flat surface opposed to the blade, and made of a resilient and heat resistant material, such as silicone rubber or felt.
If the articles to be packaged have a greater height, it is conventional to use a blade having a greater projection from the heater bars, such as 0.06 to 0.07 inch, and a cutting and sealing pad having a slot to receive the blade. In that case, the pad material still needs to be heat resistant and resilient. In both cases, the knife blade is positively locked by engagement with screws extending through close fitting openings through the blade and heater bars. A blade having a different projection is conventionally substituted when shifting between packaging articles requiring a short blade projection and articles requiring a longer blade projection. This requires removing all the blade-holding screws and reinserting them to hold the substitute blade.